As communication requirements of users increase, a growing number of cellular communications systems emerge, such as a UMTS (Universal Mobile Telecommunications System, Universal Mobile Telecommunications System) system, an SAE (System Architecture Evolution, System Architecture Evolution)/LTE (Long Term Evolution, Long Term Evolution) system, a WiMAX (Worldwide Interoperability for Microwave Access, Worldwide Interoperability for Microwave Access) system, and a CDMA (Code Division Multiple Access, Code Division Multiple Access) system.
In the prior art, in a cellular communications system, UEs (User Equipment, user equipment) mainly include single-card mobile phones and dual-card dual-standby mobile phones. The dual-card dual-standby mobile phones may be classified into dual-card dual-standby single-pass mobile phones and dual-card dual-standby dual-pass mobile phones according to operating principles of the dual-card dual-standby mobile phones. A main difference between “single-pass” and “dual-pass” lies in whether two cards of a dual-card dual-standby mobile phone can perform concurrent communication. For a “dual-pass” mobile phone, if the two cards in the mobile phone separately belong to different cellular communications systems, the two cards are independent; therefore, the two cards may separately perform, according to respective communication procedures, communication, that is, transmission of uplink data and downlink data.
By using the foregoing procedure, however, the service transmission efficiency is relatively low.